Role of extracellular polymeric substances on biocorrosion initiation or inhibition
Oil and gas industry is built of complex systems, which are vulnerable to microbial activity. Investigating microbially influenced corrosion (MIC) in order to improve the understating of this process constitutes an immense challenge. Microorganisms accumulate on the steel surface, forming biofilms embedded in extracellular polymeric substances (EPS). EPS provide the reaction space for the metal–surface interactions. The serious economic impact of MIC has lead to the understanding that development of efficient solutions strongly depends on application of multidisciplinary approaches. This study was focused on characterising the diversity of microorganisms present in the oil and gas field and on the assessment of the influence of bacterial EPS on biocorrosion processes. The first main goal was achieved by use of culture–dependent and molecular biology techniques. For the second goal, the sulfate reducing bacterium Desulfovibrio alaskensis AL1, was used as a model organism. An extraction protocol of EPS secreted by this bacterium was developed. Isolated EPS were used for further investigations, which included i) its composition analysis, ii) studies of the influence of carbon steel and flow conditions in a bioreactor on its secretion patterns and iii) its influence on the steel stability, which was investigated by means of corrosion potential monitoring, linear polarisation and electrochemical impedance spectroscopy. EPS moieties adsorbed to the carbon steel were identified with use of X–ray photoelectron spectroscopy.